Validity of compliance calibration to cracked concrete beams in bending

The method of compliance calibration for estimating crack growth in notched beams of metallic materials and nonmetallic materials such as rock has been used extensively with success. This method has also been used with concrete, but recently its suitability for this material has been questioned. The validity of this method has been evaluated using concrete beams in three-point bending in which the crack surface is revealed by a dye-penetrant technique. The results of this study, which utilized twelve specimens precracked to varying depths and thirteen companion specimens using 0.076-mm thick Teflon notches of various depths, are presented. It was found that the compliance estimates of crack length agreed exactly with the actual length for the beams with Teflon notches. For the precracked beams the compliance estimates for crack length were in good agreement with the actual length observed at the beam surface (thus confirming previously reported results) but were greater than the average crack length revealed by dye.